Construction technology has succeeded in developing a more sealed and energy efficient structure (e.g., residential dwelling, office building, etc.). Internal air, which once escaped from the structure through cracks around windows and doors and elsewhere, is now trapped within the structure. As a result, negative air pressure can be generated inside the structure in some circumstances. The negative air pressure may, in some circumstances, result in air being drawn into the structure in a manner that is unintended or unsafe. Therefore, even though the tightly sealed structure may save energy and be less costly to own, the resultant negative air pressure caused thereby may lead to undesirable side effects.